It is known to fit the rear window opening of a truck cab with a sliding window assembly made up of a pair of stationary window panes mounted outboard in a window opening to define an gap therebetween, and one or two window panes retained along their upper and lower edges in guide tracks for horizontally sliding movement. In an assembly having two sliding panes, the panes slide toward one another to close the gap between the stationary panes and slide in opposite directions away from one another to an open position in which they overlap the stationary panes.
Many different power window regulator mechanisms have been proposed to allow an occupant of the truck to open and close the sliding window by actuating a switch. These prior art regulator mechanisms usually employ a reversible electric motor to drive a cable, slotted tape, or a rack-and-pinion mechanism to move the slidable panes between the open and closed positions. The regulator mechanisms of the prior art are typically integrated in some fashion with the window frame which surrounds the window assembly and/or with the guide tracks in which the sliding panes are retained. As a result, the window panes, frame and the guide rails must be specially designed to incorporate the regulator system. Consequently, a window assembly designed to be compatible with a powered regulator is substantially different from an non-powered, manually operated sliding window. This lack of commonality between the powered and manual systems complicates the manufacturing and supply situation for a truck manufacturer wishing to offer both options on a particular type of vehicle.
Regulators utilizing a cable or slotted tape drive system have been proposed for window assemblies featuring a single sliding pane. See, for example, U.S. Pat. No. 5,784,833 and U.S. Pat. No. 4,920,698. For systems having two sliding panes, however, more complicated drive mechanisms have been found to be necessary, such as threaded shafts (U.S. Pat. No. 4,995,195) or a combination of a rack-and-pinion and slotted tape mechanism (U.S. Pat. No. 5,146,712).
An objective of some regulators is to achieve a pull/pull effect, where the cable (or other flexible, inextensible member) is routed so as to apply a pulling force to the sliding pane to move it toward its open position, and an oppositely directed pulling force to move the pane toward its closed position. Such a pull/pull drive configuration allows the cables to be constructed to less exacting dimensional tolerances with a resulting reduction in cost, and also greatly eliminates friction due to binding of the cables and the sliding pane that would be present if a pushing force were applied, thereby allowing the use of a substantially smaller, less powerful and less expensive motor.
The prior art power sliding window regulators have also generally required a relatively high degree of dimensional accuracy in the interface between the window assembly and the regulator. This is a consequence of the drive components of the regulator mechanism being integrated with the window frame and/or guide rails for the sliding panes. A relatively new type of automotive vehicle window assembly, known as a "frameless" assembly, has been proposed. In this frameless window assembly, the fixed window panes are installed directly into the window opening to provide a more simple and clean appearance. Since there is no rigid frame surrounding the window panes, the dimensional accuracy and "flatness" of such an assembly depends upon the construction of the vehicle structure surrounding the window opening. Because of normal manufacturing tolerances, the surrounding structure is likely to be less dimensionally precise than a traditional, separately fabricated window frame.